


Night at the Rave

by Travis_T



Category: Gravity Falls
Genre: F/F, F/M, Incest, Masturbation, Sibling Incest, Voyeurism
Language: English
Status: In-Progress
Published: 2020-08-30
Updated: 2020-08-30
Packaged: 2021-03-07 00:42:06
Rating: Explicit
Warnings: Underage
Chapters: 1
Words: 4,584
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26198041
Author URL: https://archiveofourown.org/users/Travis_T/pseuds/Travis_T
Summary: Set in the Gravity Falls universe, Mabel has been invited on a girl's night out by Wendy, a night that Dipper comes to realize won't be all that tame.
Relationships: Dipper Pines/Mabel Pines, Wendy Corduroy/Dipper Pines, Wendy Corduroy/Mabel Pines
Comments: 3
Kudos: 23





	Night at the Rave

"I think that's good, Dipper," Mabel said with a giggle.

"I just wanna make _really_ certain that it won't come off," Dipper said as he continued to press the electrical tape down so that the adhesive would hold. It seemed like it was pretty tightly placed, but it wasn't exactly made to stick to skin for long periods of time. Besides, he thought as a bead of sweat rolled down the side of his head, who knew when he'd get to touch another breast again.

Dipper's heart had been pounding non-stop since he walked in on his sister getting ready for her girl's night out with Wendy and Tambry. Just the sight of Mabel standing in front of the bedroom mirror wearing nothing but her underwear, clumsily working to apply the little strips of electrical tape over her erect nipples, had struck him dumb to any sense of propriety. It felt like a full minute had passed before Mabel noticed him gawking at her from the doorway like some kind of pervert. He winced when she called out his name, expecting to catch a shoe to the face but, to his surprise, she actually wanted his help getting ready.

And _that_ was how he found himself in his current predicament: poking and prodding at his twin sister's surprisingly swollen breasts. He'd replayed the events leading up to this situation in his head over a dozen times already and he still couldn't believe it was actually happening. What's worse, he had to keep making himself replay the events, or else he found himself thinking some very unbrotherly thoughts about his sister. Thoughts about how womanly she'd become. It seemed like only a few weeks since they went swimming at the pool together, but he could've sworn she was as flat as always underneath her bathing suit. Maybe he hadn't been paying enough attention though. He grimaced, really wishing he could stop paying so much attention right now. It wasn't that they were necessarily big after all, just bigger than he'd expected. And to top it off, they were just so soft and springy, bouncing his hand back no matter how hard he pushed on them. Kind of like-

"Ouch," Mabel yelped. "Dipper, you're being too rough!"

"Oh! Sorry," Dipper exclaimed pulling his hands back quickly. He'd gotten so lost in exploring his sister's body that he hadn't realized how hard he was pressing. "Are-Are you okay?"

"I'm sore." Mabel made a pouty face and kneaded at her chest gently. "But hey, it looks like you got these boys suckered on tight!" Abandoning the wounded puppy routine, Mabel jumped up and started checking Dipper's work in the mirror. "And perfectly centered too! Are you sure you don't have OCD, bro?"

"What, me? Nah, not a chance. Just--uh... making sure no one else can see your... you know. Is it weird that I saw them?" Dipper winced, wishing he hadn't said anything. "Was that... weird at all, to you?" Why was he making it worse!? "Just because, I'm... you know... a boy?"

"Aww, is little Dipper having weird thoughts about his big sister?"

"A-As if! And you're only older by five minutes!"

"Ha, c'mon, Dipper," Mabel said walking over to the closet without a shred of self-consciousness about still being in her underwear. "We're twins! You know you don't count as a boy to me." Dipper sighed in relief at hearing that. He loved Mabel and didn't want anything to get weird between them just because they were getting older. "Besides, the whole point of putting these on is so other boys will see them." All relief Dipper was feeling immediately vanished from his mind. "Boys who totally _do_ count!"

"Wait, what boys? Who counts!?"

"I dunno: strangers, maybe some of Wendy's friends, but it's a rave so there's gotta be some total cuties that are going to show up!"

Dipper felt like he'd been hit with a brick between his legs. Not only at the prospect of a bunch of random guys seeing Mabel barely covered chest, but older guys too!? And Wendy's friends? That could mean anything from Thompson to Robbie!

"Are you sure about this thing tonight? I'm not sure I'm comfortable with a bunch of guys seeing you so... _exposed_."

"Oh c'mon, Dipper," Mabel chided while rummaging around in their closet. "It's not like I'm going to be naked or anything." Oh thank God, Dipper thought clutching his chest. "I'll be wearing _this_!"

"That's..." Dipper looked his twin up and down, taking in the full effect of her outfit as she emerged from the closet. From the neck up it was nothing out of the ordinary, cute little heart-shaped earrings, a purple headband, her rainbow sweater. And that was where all normalcy ended! Her sweater had been hemmed in so that it stopped short of her breasts, leaving them completely exposed if not for the perfectly centered x's made of black tape that Dipper had helped her apply. His vision wavered as he traced his way down her supple mid-riff until it ended in a pair of short-shorts so tiny that they may as well have been underwear. Her actual underwear was also visible, the waistbands hiked up so high that they rested half-way up her torso, far above the hem of her pants. He could only imagine how snugly taut they were beneath her pants, and he found himself gulping as he wondered if he could hike them up any higher.... The outfit wasn't done there though. Her thighs were just as bare as her stomach, and so very soft and shiny looking in the room's light before disappearing into a pair of bunched up, rainbow tube socks that matched her sweater, and a pair of white sneakers that lit up in a splash of colors with each step. "That's even worse!"

"Gah, don't be such a prude." Mabel turned her back on Dipper with a dismissive wave and started touching up her make-up. "Besides, this is nothing compared to what Wendy'll be wearing."

"W-what Wendy'll be wearing? Over here!? Tonight!?"

"Heh, I guess I know where your mind is right now," Mabel's reflection smirked at Dipper. "Don't get too excited though, you probably won't get to see it because--Oh! That reminds me: Can I borrow your vest? Wendy said we have to keep ourselves covered until we get inside."

"Sure, but wouldn't it make sense to just wear one of your other sweaters instead?"

"Dipper, girls like when a guy just says yes sometimes, so don't ask so many questions!"

" _I thought I didn't count_ ," Dipper grumbled under his breath. Really though, he thought to himself, that outfit was too much. Even now with her back turned, he found his eyes tracing their way up and down her bare back. And if he looked at the reflection, he could still comfortably admire his _craftsmanship_ pasted to her chest. As he stole glances at Mabel's face to make sure she wouldn't catch him looking, Dipper accidentally caught sight of his own beet-red face in the mirror and came to the realization that a part of him wished he hadn't done as good of a job covering up her nipples as he had. God, what was wrong with him? She was his sister for crying out loud. Just the thought sent butterflies racing through his stomach. It was so wrong, what he was feeling right now, but even so, he couldn't remember the last time he had ever been this excited. Or this hard.

He shifted a bit where he stood, hands feeling around tentatively through his pockets while staring at his sister. Making as little outward movement as possible, Dipper made contact with his swollen member that had been so painfully tucked into his waistband until now. He couldn't help himself, he rationalized as he stroked it down once. Really it was a testament to his own willpower that he'd lasted this long without exploding, he thought as he stroked back up. And even though it was wrong, and that just the idea of Mabel catching him in the act terrified him more than anything he could imagine, he couldn't possibly bring himself to stop after just that. He swallowed to hold back a moan as he picked up the pace on himself, his furtive touches sending shivers down his legs and into his knees. He needed this. He needed _at least_ this. A wet spot began to form on the inside of his pocket, little strands of pre-cum sticking to his hand as he pumped. Mabel had yet to notice a thing as she continued preening guilelessly in the mirror. Dipper could feel he was close. His legs wobbled, knees buckling under him as he released all his pent up yearnings into his cargo shorts.

_KNOCK KNOCK KNOCK_

Dipper jumped, at the sound coming from the door downstairs, yanking his hands out of his pocket in a rush and falling to the ground.

"Startle much," Mabel laughed while applying her eye liner. "That's probably just Wendy and Tambry. Will you tell them I'm almost ready?"

"Yeah! Yes, of course," Dipper said trying to hide how flushed he was, as well as what he'd just done. "On it, Sis." He scrambled to his feet and rushed to the door rather quickly, making sure to turn and hide his swelling from Mabel's view. He paused in the doorway, eyes tracing down to the mess he'd made of his pants. " _I'm such a fucking creep._ "

As soon as Dipper was out of the room he rubbed down his pants as best he could to hide his shame. He was fortunate in that it wasn't especially noticeable, less so even after he pulled his shirt down a bit, but there was no hiding from the encroaching disgust and self-hatred he felt at what he'd just done. As he trodded sullenly down the stairs towards the front door, his conscience assailed him with rebukes. She was his sister for God's sake! That was disgusting! What was he, some kind of animal?

_KNOCK KNOCK KNOCK_

"Jesus H. Christ," Grunkle Stan shouted from the living room. "Can't a man enjoy the television that he stole fair and square in the comfort of his own home!?"

"I've got it, Grunkle Stan." Dipper shook the negative thoughts from his head for the moment as he picked up his pace to answer the door.

KNOCK KNOCK KNOCK

"I'm coming, I'm coming, just relax-"

"RAVE NIGHT!!!" Dipper's eyes bulged as he opened the door and was blasted with the full force of the view in front of him. Tits. Wendy Corduroy, _the_ Wendy Corduroy, was standing in the doorway wearing Robbie's hoodie, and she was spreading it wide open to give Dipper the clearest possible view of her breasts that he'd ever had! The only thing obscuring his view was a shredded blue top that hung in long tassel-like strands over her chest, but that left absolutely nothing to the imagination. "Whoops! Sorry dude, thought Mabel was gonna open the door," Wendy said with a chuckle pulling the hoodie back shut around her perfect body. "Guess you can consider that a thank you for being such a little gent, tho."

"I-I-he-I-um-he."

"You broke him," Tambry said from behind Wendy, startling Dipper out of his reverie. As per usual, her eyes were glued to her phone while she texted with lightning speed about who knew what. Instead of her usual attire though, she was wearing some kind of yellow poncho. Mabel had mentioned that they needed to keep themselves covered until they got to the rave. While he was blankly staring at Tambry, wondering what her outfit might be underneath the poncho, she shifted, lifting her hand to brush back her bangs and giving Dipper the barest glance of her outfit. Nothing but skin and fishnet.

At this point, Dipper didn't think he could actually be blushing any harder than he was. The only step up from where he was would be his head completely exploding off of his shoulders like some B horror movie.

"You do seem a bit stressed out," Wendy said, leaning forward to feel his forehead with the back of her hand, her other hand still clutching Robbie's hoodie closed. "Oh wow, you're burning up! Are you feeling okay, dude?"

"Fine!" Dipper jumped back and angled himself away from the girls, painfully aware of his rapidly inflating member and how close they were to him. "I'm fine! Mabel's upstairs! G-go right ahead!"

"Are you sure?" Wendy leaned in close over Dipper's shoulder, so close he could feel the warmth of her breath hitting his ear.

"He said he's fine, Wendy," Tambry said breezing past them towards Mabel's room, eyes still glued to her phone. "We're going to be late if you keep wasting time with him."

"Geez, what crawled up her ass," Wendy whispered under her breath. "Seriously though, just let me know if you need anything, kay?"

"S-sure thing, Wendy," Dipper managed to squeak out before watching Wendy dash up the stairs after Tambry. Even when she was leaving he couldn't take his eyes off of her, or her rear that was squeezed so tightly into a pair of cut-off jeans that he thought they might rip under the pressure. He felt faint. Deep breaths, Dipper, deep breaths! He didn't even care if she caught him staring, at this point it was all he could do to keep himself from dropping his pants and going nuts after what he'd just seen.

As soon as Wendy rounded the corner at the top of the stairs, Dipper heard the upstairs door slam slut behind her. For him, it was a like a starting pistol. Dipper raced up the stairs as quickly as he could, trying to minimize the noise he was making only as a secondary goal. What was he really expecting once he was there though? The door was already closed after all, he'd most definitely seen all he was going to get to see, and trying to peek on them now was practically a death sentence if he got caught-

"Oh my God," Wendy exclaimed. "Mabel, you look so hot!"

"Whoa," Mabel said. "You're squishing me up against your boobs, Wendy."

"Ha, should I squish up against yours too? Tambry take our pic!"

Dipper dropped to the floor faster than a recruit doing push-ups, lining up his eye with the gap between the door and the floor. Something! He needed to see something dammit! Anything!

"Sigh... say cheese...," Tambry said.

"Cheese, motherfucker," Wendy shouted excitedly.

"Chees--ahhh!" That sounded like Mabel shouting mid-cheese. "Wendy, you pinched me!"

"Ha, just playing with you, girlfriend!" Feet! Nothing but feet in sight! It wasn't fair! Damn you door!!!

"Let me see, let me see! Ooohhhh," Mabel said in awe. "We look so hot!"

"We don't just look hot, we look like some bad bitches! We're gonna tear this night up!"

"Posting...," Tambry said. "#justacoupleofsluts...."

"Wait, you're actually posting that," Mabel exclaimed. "What if my parents see it?"

"Nah don't worry, this is just for my exclusive account," Wendy said. "Nothing but a bunch of hot dudes on here, right Tambs?"

"More like horny simps," Tambry said.

"Haha, gross," Mabel laughed. On the other side of the door, Dipper was already furiously pounding away at his phone with a fervor that would put Tambry to shame. New Snapchat account, fake name, alt e-mail address. Locked and loaded. He pulled up the map feature and searched for people near him. If Wendy had her location address on, and God willing she did, she should show up as right next to him on the map. Dipper could hear the girls moving on the other side of the door. Looking back at the phone it was still in loading hell, searching for people nearby. If they caught him like this, it'd be trouble. Quietly he raised himself up off the floor, hyper conscious of every creak in the floorboards as he shifted his weight. As soon as he was on his feet, he backed up carefully towards the staircase, feeling out every step before putting his weight into it. Looking back at the phone, he saw that it had finished searching, and there were accounts with their locations on near him. Patience, he cautioned himself. After he was three steps down on the staircase, he abandoned all sense of stealth though and rushed down, turning all focus towards his phone. It looked like there were 3 accounts active near him. ShootingPineStar. Mabel's for certain, he was pretty sure he recognized it from the one time he'd actually used Snapchat in the last year. The second one was DaddiMoarBux69 and--Eugh! Grunkle Stan!? That avatar definitely looked like him without his shirt on. Dipper wavered a moment, wondering if what he was doing could ever be worth suffering that sight. Shake it off man! One left. The last one was... Corduroy_Girl97! Yes! That had to be Wendy's account!

Dipper cheered silently, pumping his fists in the air in exultation. Almost there, now he just had to add her... No! The account was private of course. She'd have to approve his friend request before he could get in. He pulled open his profile page again and looked it over, biting his lip. He had just made up a name on the spot, shouldn't have any correlation to him, surely that was good enough. No avatar though. Dipper did a quick search for 'hot college guys' and after immediately being assailed by nude pics, he switched over to safe search and was able to grab a nice, clean face shot. Okay, finger's crossed, he prayed to himself. Here goes. Dipper pressed the 'send friend request' button, his thumb leaving a sweaty print on the phone screen.

There... he'd done it. He gulped. He'd really done it. And that was all he could do, right? Wendy would deny it, or not see the request for days. It's not like she was Tambry after all. And now that Dipper was downstairs he wouldn't even be able to eavesdrop and find out what she would think if she did see it. Either way though, she wouldn't know it was him, so no harm there... right?

....

It felt very silent suddenly. Dipper couldn't hear the girls' voices from upstairs anymore. Could he hear them from downstairs before? He couldn't remember, but that only accelerated his anxiety. Had he been too obvious with the friend request? There was no way they could tell it was him of course. Oh God, he thought. What if he left the location on!? Then Wendy would easily know it was him, or maybe Grunkle Stan, and then--

There was a loud slam upstairs as the bedroom door swung open, followed by a swell of noise as the girls all came clambering downstairs. Dipper winced and raised his arms to shield himself, certain that they had found him out and that he was about to experience the beating of his life!

"Later bro," Mabel yelled excitedly rushing out the door.

"Peace, loser," Tambry said, following suit at a slower pace.

"Take it easy, Dip," Wendy said, pulling Dipper in for a playful noogie. "Sorry you couldn't come with us this time, but we'll plan a fun night you can come on next time!"

"Y-yeah," Dipper said, lifting a hand to his cheek that had been pressed up against her chest. "H-have fun!" Before he had even finished his sentence though, Wendy was out the door and hopping into the car with Mabel and Tambry.

Dipper stood unblinking at the front door. His heart's pounding eventually slowing down enough for him to hear Grunkle Stan grumbling at the TV in the other room.

"Ha... ha...," Dipper clutched his chest panting. They hadn't figured it out. He was safe and clear. Really though, that had been too close, what was he thinking trying something that risky? He looked back down at his phone.

"No way," he breathed in disbelief.

_Corduroy_Girl97 has accepted your follow request._

Dipper's heart rate immediately started beating faster. There was a blue outline around her avatar. She had a story up. Glancing over to the den, he saw that Grunkle Stan was still busy watching TV and paying no attention to Dipper. Dipper raced upstairs again, willfully ignoring the exhaustion in his legs from going up and down so many times. Straight to his room, he pulled the door shut, and locked it just to be extra certain. Leaning back against it, he sank to the floor. Moment of truth, here goes, he thought as he pressed the icon to pull up her story.

The first pic that came up was an up close selfie of Wendy. Pretty standard, and she was beautiful... but that's not what Dipper came for, he rationalized as he clicked to the next image. More of the same, another close up selfie, this time with some text about how bored she was this morning. Dipper clicked through the next, and the next one, and the next one. Darn it! Was this just her normal Snapchat after all? He'd be so excited, but he could feel his heart sinking as he clicked through selfie after selfie after nude selfie.

Dipper's eyes went wide. Wendy was standing in her room, angled to the side with not a single piece of clothing on. Reaching down, Dipper gripped his man handle through his pants and began massaging the growing lump. From the way she was positioned, he could only make out the curve of her breasts and the side of her butt, but it was more than he'd seen until earlier today, he thought remembering how she had greeted him at the door. Dipper unzipped his pants carefully, exposing himself to the open air. There was a light floral scent hanging in the air, and he wasn't sure whose perfume it was, but he took a deep breath of it and gripped himself firmly with his right hand, while clicking forward to the next picture with a shaky left hand.

This time it was a shot of Tambry, and in her rave gear no less. Dipper hadn't gotten a good look at it before, but now, in the privacy of his own room he gave it a thorough examination while working at himself in a circular motion. The shirt of her outfit was made of a mesh material and barely covered anything, giving anyone who saw a clear look at her large nipples. Unlike Wendy, Tambry's were a dark, chocolate brown color and were oval shaped too. Would she be able to stay as nonchalant as usual if he were sucking on them? Tantalizing as they were though, the most striking part of her outfit by far was a big fuzzy hat with a pair of cat ears on top of it. Dipper thought it a bit odd, but it was strangely exciting and matched the fuzzy, knee-high leggings she had on as well. It kind of made her look like a furry actually, Dipper thought, feeling a bit guilty about thinking it was attractive, and a bit curious about how far Tambry's interests went. That was something to consider another time he thought, clicking forward.

And there it was, the picture he'd been waiting for. Wendy _and_ Mabel. They were both dressed in their rave gear, and were cheek to cheek together in a hug, as well as breast to breast Dipper noted as he started stroking himself in earnest. However, while one of Wendy's arms was wrapped around Mabel's shoulders, her free hand had snuck it's way up to Mabel's black tape pasty and was pinching at the nub beneath it mercilessly. Dipper could still hear Mabel's yelp from earlier, and the shocked look on her face in the picture matched the sound he remembered perfectly. Surprised and embarrassed, but with an excited smile tugging at the corners of her mouth.

Dipper swallowed the drool collecting in his mouth and started pumping himself like a jackhammer, savoring the reward he had sought. It was strange though, he thought as he pounded away at himself. Wendy was cool, sexy, and gorgeous, and doing nothing to cover her tits in this picture, but right now his eyes couldn't help wandering over to his sister. More than once he'd stopped himself and swiveled his eyes back to Wendy's ample bosom, hanging bare and free in her outfit, a sight he had spent hours fantasizing over. Mabel wasn't even showing as much skin, and he'd already seen her like that. So why did he keep fixating on her? And not even on her body, but on her face. Before today, he'd never looked at her that way, and while he was still a little bit disgusted with himself, now that he was left alone to confront this desire, he found himself caring less and less. Instead he just wondered what she was doing without him?

Dipper stopped his movements abruptly, loosening his grip on himself as he looked morosely at the Snapchat picture in front of him. He felt sick to his stomach. He didn't want to be alone in his room fapping off to a picture of Wendy and his sister. He wanted to be there.... With them.

Backing out of Wendy's Snapchat story, Dipper saw that the map had updated Wendy's location. She had accepted his friend request after all, now he got to see where she was so long as she kept her location on. Her icon had moved from being at the Mystery Shack to someplace down in town. That must be where the rave is happening, he thought.

...

That must be where the rave is happening!

Dipper jumped to his feet, a new plan forming in his mind. It was risky. Way riskier than any of the stupid stuff he'd done so far this night, but anything would be better than staying here and wallowing like this! He glanced at himself in the mirror. First things first, he'd need a change of clothes. Diving into Mabel and his' shared closet, Dipper dug through piles of clothes looking for options. Unsurprisingly, he found nothing that would do, well, not unless he wanted to go dressed like a girl. He shuddered at the idea, but tucked it away as a back-up if all else failed. Urrrggg! Why couldn't Mabel and him ever wear a Summerween outfit that was actually cool!?

There had to be something somewhere though! Dipper raced out of the room, tearing a desperate trail through the Mystery Shack as he searched for anything passable he might use.

"Hey kid, keep it down already!" Grunkle Stan shouted, but he barely even registered the complaint as he scoured the Mystery Shack. This hat? Too recognizable. These glasses? Nah, I can't wear my sunglasses at night. What is this? Some kind of fur--

And then it dawned on him. Dipper grimaced, remembering the shame he'd last felt when Grunkle Stan had forced him to wear that thing in front of tourists so they could earn a quick buck. He'd absolutely refused the mask before, opting for a headband with little ears on it instead, but this time... This time any shame he may have felt was nothing compared to the desire burning in him. And besides, he thought remembering Tambry's outfit, it very much looked like something to wear at a rave.

**Author's Note:**

> Hey all, this is my first attempt at writing fanfiction in a long while. Long story short, I got a bit tipsy and started doodling out naughty pics based on an idea that sort of popped into my head. Didn't want to release the pics without any context though, and I'm too lazy/inept to actually make a comic, so I decided I'd write up some smut to fill in the backstory before finishing and posting the pics. Hope you guys enjoy it!


End file.
